Comparative Characterization of Polysaccharides from Rosa roxburghii Tratt. Fruits Collected from Eight Major Producing Areas of Guizhou: Structure, Physicochemical Properties, and In Vitro Bioactivity

Abstract

Polysaccharides from Rosa roxburghii Tratt. (RRTP) are predominantly pectic and are considered core bioactive compounds of the fruit. In this study, RRTPs were extracted from fruit of the cultivar ‘Guinong 5’ collected from eight major production areas in Guizhou, China, to evaluate source-associated differences in pectic structural features, physicochemical properties, antioxidant capacity, and inhibitory activity against α-amylase and α-glucosidase. Extraction yields ranged from 3.29% to 4.64%. All RRTPs exhibited typical pectic characteristics, but significant differences were observed in uronic acid content, mo-nosaccharide composition, the distribution of homogalacturonan (HG) and rhamnogalacturonan-I (RG-I) domains, molecular weight, particle behavior, and thermal properties. Among the tested samples, RRTP from Congjiang County (RRTP-CJ) showed the highest galacturonic acid content (49.72 mol%) and one of the lowest molecular weights (80.6 kDa). It also exhibited the strongest DPPH•, ABTS• + , and O 2 • − scavenging activities with half-maximal inhibitory concentration (IC 50 ) values of 0.394, 0.300, and 0.452 mg/mL, respectively. RRTP-CJ also showed the strongest Fe 2+ -chelating activity, with a half-maximal effective concentration (EC 50 ) of 0.671 mg/mL, and the strongest α-amylase and α-glucosidase inhibition, with IC 50 values of 2.425 and 0.747 mg/mL, respectively. Correlation analyses indicated that uronic acid content and HG abundance were positively associated with antioxidant capacity and carbohydrase inhibitory activity, whereas higher molecular weight and extensive RG-I branching were negatively associated with these effects. Principal component analysis further distinguished highly bio-active samples characterized by lower molecular weight and a higher content of galacturonic acid. Overall, substantial source--associated heterogeneity was revealed among RRTPs, and RRTP-CJ was identified as a promising raw material for functional food ingredient development. These findings should be interpreted within the scope of a single cultivar and harvest year, providing a basis for raw-material selection, standardization, and subsequent multi-year validation.